Difference Between Turbofan and Turboprop

Turbofans and turboprops are both the variations of turbojets, which is an air breathing gas turbine engine. The major problems related with turbojets are low efficiency at subsonic speed and higher levels of noise pollution. To overcome these discrepancies, a lot of ingenious designs have been introduced over the years, with turbofans and turboprops being some of the most commonly used and the efficient ones.

There are quite a few pronounced differences between the two designs.

In a turbofan, the shaft work is used to drive a fan which sucks in huge quantities of air, whereas in a turboprop, the turbine engine is used to drive a propeller.

In a turboprop, the thrust generated for propulsion is produced by the propeller only, whereas in the turbofans, a combination of bypass air and the air used for combustion is used.

The range of operation of turboprop is limited only to subsonic speeds, but a turbofan can be used efficiently at both subsonic and supersonic speeds.

Instructions

  • 1

    Turbofan

    A turbo fan is variation of the turbojet in which the shaft work is used to drive a large fan which sucks the air at a pressure. Part of the air, depending on the bypass ratio, get compressed after passing through the stages of an axial compressor and is used in combustion. The exhaust gases produced by this are then directed at the blades of a turbine, which rotates the shaft. The shaft work is used to drive the fan. The exhaust gases are then directed through the nozzles where their velocity increases and  help in propulsion along with the air coming directly through the fan.

    This type of gas turbine is very efficient and the noise pollution is minimal.

    Image courtesy: popsci.com

  • 2

    Turboprop

    Turboprop is also a variation of turbojet gas turbine engine, but can only operate at subsonic speeds (below the speed of sound).

    In this engine, the shaft work is used to drive a propeller, which sucks the air. This propeller is attached to the shaft through a reduction gear mechanism, and its blades are usually of constant speed (variable pitch) type.

    One major feature of the turboprops is that there is negligible propulsion due to the thrust of exhaust gases, as was the case in turbojets and turbofans. These engines are totally dependent on propeller reaction to produce the thrust which propels the craft.

    Image courtesy: 2.bp.blogspot.com

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